In the semiconductor process, a charged beam (hereinafter, referred to as primary beam) such as an electron beam or an ion beam is irradiated on a sample, and signals from a generated secondary charged beam (hereinafter, referred to as secondary beam) such as a secondary electron beam are acquired, wherein an electron beam length measurement apparatus that measures the shape and size of a pattern formed on the sample, and an electron beam inspection apparatus that inspect the existence or nonexistence of defects on the sample are employed.
In such a charged particle beam apparatus, enhancing the speed to process the sample, that is, enhancing the speed to inspect the sample is an important problem together with the enhancing the sensitivity to detect defects on the sample. In order to solve this problem, a multi-beam type charged particle beam apparatus in which plural beams is employed has been proposed. For example, in Japanese Patent Application No. 2006-144934, a multi-beam type charged particle beam apparatus is disclosed, wherein an electron beam emitted from a single electron gun is separated into plural beams, and the plurality of beams, which are formed individually by focusing lenses arranged like an array, are projected and scanned on the sample using a single optical element.